A mass of 2kg on a surface ( μ = ½) is connected to a second mass of 4kg over a frictionless pulley as shown above. If the acceleration due to gravity is 9.8m/s² the masses will

John Perolski
September 03, 2023

 Physics Jamb, Waec, Neco Past Questions & Answers on FRICTIONAL FORCE


QUESTIONS 12: A mass of 2kg on a surface ( μ = ½) is connected to a second mass of 4kg over a frictionless pulley as shown above. If the acceleration due to gravity is 9.8m/s² the masses will 

A. Accelerate at 4.9m/s² 

B. Remain stationary 

C. Accelerate at 9.8ms'2 

D. Accelerate at 19.6ms" 

E. Accelerate at 39.2m/s²

ANS. A JAMB 1981

NB: Tension and acceleration are always constant. Thus:

Horizontally,

T - μN = m1(a)

T - μ(m1)g = m1(a)

T - ½(2)(10) = 2a

T - 10= 2a •••> (1)

Vertically,

(m2)g - T = (m2)a

4(10) - T = 4(a)

40 - T= 4a •••> (2)

From (1),

T= 2a + 10 •••> (3)

Put (3) in (2)

40 - 2a - 10= 4a

30= 6a

a= 5m/s²

From (3)

T= 2(5) + 10= 20N

For the question. "...what then would happen to the masses?"

Mass 4kg would pull mass 2kg with an acceleration of 5m/s² 

and tension of 20N.